1. Field of the Invention
The present invention relates to wireless communication, and more particularly, to an apparatus and method for transmitting data in a wireless communication system.
2. Related Art
The IEEE (Institute of Electrical and Electronics Engineers) 802.16 standard provides technology and a protocol for supporting broadband wireless access. The IEEE 802.16 standard had been standardized since the year 1999, and IEEE 802.16-2001 was approved in the year 2001. IEEE 802.16-2001 is based on a single carrier physical layer called ‘WirelessMAN-SC’. After that time, in the IEEE 802.16a standard approved in the year 2003, ‘WirelessMAN-OFDM’ and ‘WirelessMAN-OFDMA’ were further added to the physical layer in addition to ‘WirelessMAN-SC’. After the IEEE 802.16a standard was completed, a revised IEEE 802.16-2004 standard was approved in the year 2004. In order to correct bugs and errors of the IEEE 802.16-2004 standard, IEEE 802.16-2004/Cor1 (hereinafter referred to as IEEE 802.16e) was completed in the year 2005 in the form of ‘corrigendum’.
FIG. 1 shows an example of a frame structure in an IEEE 802.16e system. A frame is a data sequence during a fixed time used by physical specification. For the frame, reference may be made to Paragraph 8.4.4.2 of IEEE standard 802.16-2004 “Part 16: Air Interface for Fixed Broadband Wireless Access Systems” (hereinafter referred to as ‘Reference Document 1).
Referring to FIG. 1, the frame includes a downlink (DL) frame and an uplink (UL) frame. Time Division Duplex (TDD) is a scheme in which UL transmission and DL transmission share the same frequency, but they are generated at different times. The DL frame is temporally earlier than the UL frame. The DL frame is started in the sequence of a preamble, an FCH (Frame Control Header), a DL-MAP, an UL-MAP, and a burst region. A guard time for distinguishing the UL frame and the DL frame is inserted into a middle part (between the DL frame and the UL frame) and the last part (next to the UL frame) of the frame. A TTG (transmit/receive transition gap) is a gap between a DL burst and a subsequent UL burst. An RTG (receive/transmit transition gap) is a gap between the UL burst and a subsequent DL burst. The preamble is used for initial synchronization between a base station and user equipment, cell search, a frequency offset, and channel estimation. The FCH includes information about the length of a DL-MAP message and a coding scheme of the DL-MAP. The DL-MAP is a region where the DL-MAP message is transmitted. The DL-MAP message defines the access of a DL channel. The UL-MAP is a region where an UL-MAP message is transmitted. The UL-MAP message defines the access of an UL channel.
Today, an IEEE 802.16m standard (i.e., a new technology standard) is in progress on the basis of the IEEE 802.16e standard. In standardizing IEEE 802.16m, the existing system parameters may be newly defined. Accordingly, frame structures need to be configured so that the newly defined system parameters can be efficiently supported.
Furthermore, IEEE 802.16m (i.e., the newly developed technology standard) has to be designed so that it can support the previously designed IEEE 802.16e standard. The newly designed system technology has to be configured so that it efficiently covers the existing technology (i.e., IEEE 802.16e) and operates. This is called backward compatibility. A frame to satisfy backward compatibility for the existing system is a dual frame. The existing system may refer to an IEEE 802.16e system, and a new system may refer to an IEEE 802.16m system. Accordingly, in the IEEE 802.16m system, research is being carried on frame structures capable of satisfying backward compatibility for the IEEE 802.16e system.
Furthermore, a system profile based on a conventional IEEE 802.16 standard supports only the TDD (Time Division Duplex) scheme, but attempts to support the FDD (Frequency Division Duplex) scheme in which UL transmission and DL transmission are performed at different frequency bands at the same time. Accordingly, for convenience of a system design and share of hardware, it is necessary to design an FDD frame structure having commonness with a TDD frame structure.